Composite materials are increasingly used as substitutes for conventional materials such as aluminum and steel alloys in various structural components due to the generally high strength-to-weight ratio inherent in composite materials. Composite materials may generally be comprised of a network of reinforcing fibers that are generally applied in layers, and a polymeric resin that substantially wets the reinforcing fibers to form an intimate contact between the resin and the reinforcing fibers. High speed composite layup machines are typically used to form each layer. Such machines can lay composite material at a rate of 3000 inches per minute.
A problem can arise, however, when foreign object debris (FOD), contamination or other type of tape layup anomaly is on or within the formed composite part prior to curing. For example, small amounts of entrapped or surface-adhering moisture or other types of contamination can result in delaminating and porosity of the composite material once the curing is completed. In addition, debris such as small pieces of bagging materials, Teflon tapes or breathing material used during the composite layup that becomes entrapped within a composite layer can result in delamination, porosity and wrinkles in the composite part. One particular type of FOD is referred to as a fuzzball and is generated during the manufacture of a composite part formed from layers of carbon fiber reinforced polymer (CFRP) tape. A so-called “fuzzball” consists of strands of CFRP tape that are abraded by contact with the spools holding the tape and which may randomly fall onto the surface of the composite part under manufacture. Further, other types of tape layup anomalies can occur during layup including twists, folds, untacked tows, wrinkles, bridging, etc. FOD and defect detection is currently done manually by visual inspection. Often, however, FODs and defects are either transparent or blend well with a surface color of the composite material and are thus difficult to detect visually. This manual FOD and defect detection method is thus slow and unreliable. Significantly, if the FOD materials and defects are not detected and removed or repaired prior to curing, large and expensive composite parts may be rejected during nondestructive testing.
One-piece composite parts are presently used in many applications, including parts for commercial aircraft. Such parts can be very expensive to manufacture, and very small FOD materials, contamination or defects not removed during the buildup phase of such a part can result in a manufacturing defect that requires the repair or even rejection of the part. The repair or rejection of such parts is thus quite costly and can also result in schedule delays and inventory problems.
Accordingly, there is a need for an automated high-speed inspection system for the detection of surface and subsurface FODs, contamination and defects during the high-speed composite layup process.